Lockable lug nuts have been used on vehicle wheels to prevent tire theft and to insure the stable attachment of the wheel to the vehicle axle. The conventional lockable lug nut is available in three forms. The first form is composed of a lug nut with a hollow depression at its top with an irregularly surfaced interior insert. The lock or key with a compatible irregular surface is inserted into the nut and force applied to lock or unlock the nut threaded on the lug bolt.
The second conventional lockable lug nut consists of similar construction, though taller than the norm. The interior of the lug nut is threaded, with two opposing interior indentations located at one end of the lug nut. The key is affixed to the cavity apex of a socket, similar to that regularly used in conjunction with a socket wrench. The key has two retractable protrusions located near its base. The socket with the key, when inserted, covers the lug nut. The protrusions engage the indentations and lock the socket with key in place. Force in the form of rotary motion is then applied to fasten or unfasten the nut.
A third form of the prior art is a lug nut and washer apparatus, where the lug nut covers a key and the key engages the washer. The key is cylinder shaped with a flat disc base. A multitude of short prongs are mounted on the underside of the base. The prongs engage corresponding holes on the washer, which then abuts the corresponding holes on the washer, then abuts the key and covering nut. Force is exerted to engage the key and washer which in turn fastens or unfastens the lug nut and washer apparatus to the bolt.
These conventional lug nuts are inadequate in many respects. The locking feature is easily broken by the application of an improper key or by excessive force. Thus, the broken lug nut permanently connects the wheel to the axle and needs to be removed by a costly and time consuming process. Another problem with the conventional lockable lug nut is the difficulty in precisely applying a specified amount of force to the nut. The structure of the conventional lockable lug nuts often dictates that less than the prescribed amount of torque be applied. An application of excessive force may cause a prong to break as in the third prior art example or the irregular interior insert to crack as in the first example, as neither the prongs nor insert are strong.
Another drawback to the conventional lockable lug nut are the available keys. The ordinary lockable lug nut type has a hollow depression at its top with an irregular interior surface. An alternate arrangement is the prong form. The key's surface or prongs are arranged in a corresponding irregular manner so that a particular key can be inserted and fit only a specific locking lug nut combination. In practice there are only fifteen combinations of keys and lug nuts; thus, the variations are limited. Furthermore, it is difficult to visually determine what key will fit a particular lug nut.
A further problem with the conventional locking lug nut is the inability to adjust its weight should it be heavier than the other lug nuts used on a wheel. The wheel may become unbalanced and vehicle performance impaired. A counterweight fixed on the tire rim at a position opposite to that of the heavy conventional locking lug nut is necessary to counteract the excessive weight and to restore wheel balance.
It is therefore an object of the present invention to provide a locking lug nut which is lightweight and easily alignable.
Another object of the present invention is to provide a locking lug nut which is durable and not easily broken by either force or an incorrect key.
A further object of the present invention is to provide a lug nut which is adjustable to the desirable wheel weight.
Another object of the present invention is to provide a wide variety of lug nut and key combinations.